A "defeated" rice resistance gene acts as a QTL against a virulent strain of Xanthomonas oryzae pv. oryzae
A "defeated" rice resistance gene acts as a QTL against a virulent strain of Xanthomonas oryzae pv. oryzae
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DOI：
10.1007/s004380050941
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发表时间：
1999-02-01
期刊：
影响因子：
--
通讯作者：
Ying, CS
中科院分区：
文献类型：
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作者：
Li, ZK;Luo, LJ;Ying, CS
水稻对黄单胞菌致病变种CR 4、CXO 8和CR 6的定性和定量抗性的遗传组成。利用Lemont（粳）×特青（籼）组合的315个重组自交系（RIL）和182个分布良好的RFLP标记构建了一张完整的连锁图谱。我们定位了一个主效基因（Xa 4）和10个数量性状基因座（QTL），这些基因座在很大程度上负责RIL中抗性表型的分离。Xa 4位点的特青等位基因Xa 4（T）是对CR 4和CXO 8的显性抗性基因。由强毒株CR 6中av 1 Xa 4基因座处的突变等位基因介导的Xa 4（T）相关抗性的破坏是由于基因作用（显性丧失）和基因效应的幅度（约50%降低）两者的显著变化。尽管如此，Xa 4（T）仍然是一个隐性QTL，对CR 6有显著的残留效应。CX 08和CR 6中avrXa 4基因座处的突变等位基因导致Xa 4（T）的效应降低或“破坏”，显然伴随着对其适合度的相应惩罚。重组自交系对Xoo的抗性主要由数量性状QTL控制。大多数抗性QTL定位在同一杂交组合中鉴定出的抗白叶枯病、稻瘟病和纹枯病的主效抗性基因和/或QTL所在的基因组位置。大多数QTL对所有三个Xoo菌株的抗性水平一致。我们的研究结果表明，高水平的持久抗Xoo可能是通过多个QTL的累积效应实现的，包括“失败”的主效抗性基因的残留效应。
The genetic components responsible for qualitative and quantitative resistance of rice plants to three strains (CR4, CXO8, and CR6) of Xanthomonas oryzae pv. oryzae (Xoo) were investigated using a set of 315 recombinant inbred lines (RILs) from the cross Lemont (japonica) x Teqing (indica) and a complete linkage map with 182 well distributed RFLP markers. We mapped a major gene (Xa4) and ten quantitative trait loci (QTLs) which were largely responsible for segregation of the resistance phenotype in the RILs. The Teqing allele at the Xa4 locus, Xa4(T), acted as a dominant resistance gene against CR4 and CXO8. The breakdown of Xa4(T)-associated resistance mediated by the mutant allele at the avl Xa4 locus in the virulent strain CR6 results from significant changes in both gene action (lose of dominance) and the magnitude of gene effect (approximate to 50% reduction). Nevertheless, Xa4(T) still acted as a recessive QTL with a significant residual effect against CR6. The mutant alleles at the avrXa4 locus in CX08 and CR6 that lead to a reduction in effect, or "breakdown", of Xa4(T) were apparently accompanied by corresponding penalties for their fitness. The quantitative component of resistance to Xoo in the RILs was largely due to a number of resistance QTLs. Most resistance QTLs mapped to genomic locations where major resistance genes and/or QTLs for resistance to Xoo, blast and sheath blight were identified in the same cross. Most QTLs showed consistent levels of resistance against all three Xoo strains. Our results suggest that a high level of durable resistance to Xoo may be achieved by the cumulative effects of multiple QTLs, including the residual effects of "defeated" major resistance genes.